1. Field
The present invention relates generally to environmentally resistant germicidal systems, and more particularly the invention relates to such devices used in air and surface sterilization.
2. Description of the Related Art
One industry that is mature and economically sensitive to costs is the heating, ventilation and air conditioning (HVAC) industry. Because of the competitive nature of both the construction and HVAC industries, HVAC systems must be inexpensive to purchase and install. Of a more global interest though, is the cost to operate and maintain HVAC systems. Often, a building owner will replace an aging HVAC system as the reduction in operating and maintenance costs can offset the retrofit cost, sometimes in a matter of months.
Broad social and energy policies also favor efficient HVAC systems. In these days of electricity conservation and deregulation, it has become even more important to conserve energy consumption. Recently, entire electrical grids have shut down on very hot days in part because of the huge electrical demand from inefficient HVAC systems running at extreme capacity. Furthermore, energy conservation translates directly into improved environmental conditions and decreased reliance upon foreign petroleum.
HVAC systems are typically comprised of a cooling and heating section for, respectively, cooling and heating the air. An HVAC system will also include fans and ductwork for moving this conditioned air where it is needed. In most HVAC systems, air is drawn in, filtered, cooled and dehumidified or heated and humidified, and then delivered to a space. The greatest portion of this air is drawn from the space for recirculation through the HVAC system.
One factor impacting design and operation of HVAC systems is indoor air quality (IAQ). A major consideration in IAQ today is the amount of outdoor air introduced by an HVAC system into an otherwise sealed space. The HVAC industry and others have adopted standards for the introduction of outdoor air into spaces serviced by an otherwise closed HVAC system. These include offices, residential, commercial, industrial and institutional spaces, and modes of transportation such as cars, buses, planes and ships. In addition to controlling indoor air for occupant comfort, the goal of most HVAC systems is to provide air with reduced levels of particulate, gases and bioaerosols, be it for semiconductor, pharmaceutical or food processing facilities, hospitals, schools or offices and now the home.
Besides IAQ standards that include HVAC systems, there are numerous other standards that apply to HVAC systems, their design, construction and components. One set of standards that applies to HVAC (and other) electrical equipment has been promulgated by the National Electrical Manufacturers Association (NEMA). NEMA has published standards regarding enclosures for electrical equipment including HVAC equipment installed outdoors. A NEMA Type 4 enclosure is constructed for outdoor use and provides a degree of protection against rain, sleet, snow and the formation of ice. A NEMA Type 4 enclosure also provides a degree of protection against windblown dust, dirt, splashing water, hose-directed water and corrosion. A NEMA Type 4 enclosure should protect personnel against incidental contact with the enclosed equipment. Additional information is available from the NEMA Web site at www.nema.org.
One common use of germicidal lamps is in water treatment. The ultraviolet tubes are enclosed in a quartz sleeve. This is necessary because the water would otherwise draw heat away from the tube in the same manner as air or as in skin effect cooling.
Germicidal lamps for water treatment must have some amount of protection from the water itself. In particular, these lamps are sleeved and further isolated in some manner to be water tight against and compared to the water vessel in which the tube is installed. However, water application fixtures have not been considered or used in air treatment systems. Also, water application fixtures have not been produced for HVAC use or for air treatment use.
It is common for germicidal systems for air purification to be installed outdoors in the proximity with an HVAC systems ductwork, condenser or compressor. Outdoor installation may subject the electrical components of the germicidal system to environmental elements such as condensation, dripping water, splashing water, light spraying of cleansers, dripping oil, falling dirt, windblown dust, and windblown sand. An example of germicidal system designed to protect electrical components from harsh environmental elements is described in U.S. Pat. No. 6,372,186, Germicidal Lamp for Harsh Environments.
It is also common for germicidal systems for air purification to be installed indoors at hospitals, office buildings, food processing plants, and schools. Because such systems are not subject to harsh outdoor environments a NEMA 4× enclosure may be cost prohibitive to protect the electrical components.